CN105772016A - Nickel-based catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a nickel-based catalyst for catalytic reforming of methane and carbon dioxide to produce synthesis gas and a preparation method thereof, belonging to the field of catalytic reforming of methane and carbon dioxide to produce synthesis gas. The chemical formula of the nickel-based catalyst is Ni(Mo)/(Cex Zr _{1-x O 2} ) _y MgAl (O), wherein Ni is an active metal, MO ₃ .MgO and Cex Zr _{1-x O 2} are auxiliary Agent, Al ₂ O ₃ as carrier, wherein x/1-x=0.25-4, y=1-15%.

Description

Nickel-based catalyst and preparation method thereof

technical field

The invention relates to the field of catalytic reforming of methane and carbon dioxide to produce synthesis gas, in particular to a nickel-based catalyst for catalytic reforming of methane and carbon dioxide to produce synthesis gas and a preparation method thereof.

Background technique

At present, the large-scale utilization of methane mainly relies on indirect conversion, and carbon dioxide reforming of methane is a relatively widely used method in the application of indirect methane conversion. With the improvement of people's awareness of environmental protection, the utilization and control of greenhouse gases have attracted more and more attention. In the methane carbon dioxide reforming process, the catalyst is the core of the system. Carbon dioxide catalytic reforming of methane to synthesis gas can effectively convert carbon dioxide and methane, two major greenhouse gases, into important chemical raw materials.

Moreover, CO/H ₂ =1:1 synthesis gas can be produced by reforming methane with carbon dioxide. Over the years, researchers at home and abroad have invested a lot of manpower and material resources in the research of this catalytic reaction. But so far, the carbon dioxide catalytic reforming process of methane is still far from the requirements of industrialization. Studies have shown that when precious metals ruthenium (Ru), rhodium (Rh) and palladium (Pd) etc. are loaded on a suitable carrier, they all have higher reactivity and anti-carbon deposition properties. For example, German Patent DE9400513 discloses in After 500 hours of continuous use of the Pd/ZrO ₂ catalyst, the reactivity remains basically unchanged. However, the disadvantage of noble metal catalysts is that they are expensive and do not have economic advantages in industrialization. Among non-precious metals, nickel-based catalysts have high reactivity, but carbon deposition is serious. For example, carbon deposition will cover the surface of the catalyst and cause catalyst deactivation. It will also cause reactor blockage and increase the pressure of the catalyst bed.

Therefore, how to solve the carbon deposition and sintering of nickel-based catalysts is one of the fundamental problems in realizing industrialization.

Contents of the invention

In order to solve at least one aspect of the above-mentioned problems and defects in the prior art, the present invention provides a nickel-based catalyst for catalytic reforming of methane and carbon dioxide to produce synthesis gas and a preparation method thereof. Described technical scheme is as follows:

An object of the present invention is to provide a nickel-based catalyst for catalytic reforming of methane and carbon dioxide to synthesis gas.

Another object of the present invention is to provide a method for preparing a nickel-based catalyst for catalytic reforming of methane and carbon dioxide to produce synthesis gas.

According to one aspect of the present invention, a nickel-based catalyst for catalytic reforming of methane and carbon dioxide into synthesis gas is provided, wherein the nickel-based catalyst has a chemical formula of Ni(Mo)/(Ce _x Zr _1-x O ₂ ) _y MgAl(O), where Ni is the active metal, MO ₃ . MgO and Cex Zr _{1-x O 2} are additives, Al ₂ O ₃ is the carrier, where x/1-x=0.25~4, y = 1%-15%.

Specifically, the nickel-based catalyst includes 8% to 15% of nickel oxide and 0.2% to 0.70% of molybdenum oxide in terms of mass fraction, and ceria and zirconium dioxide account for 1% to 10% of the total mass of the nickel-based catalyst. 15%.

Further, the nickel-based catalyst uses NiMgAl-like hydrotalcite as a precursor, and the catalyst precursor is prepared in one step by a co-precipitation method, and then used after washing, drying and roasting, and performing a reduction reaction in a reducing atmosphere.

Further, the reducing atmosphere is a mixed gas of hydrogen and nitrogen, the ratio of hydrogen and nitrogen in the mixed gas is 1:1, and the reduction reaction is carried out at 900-1000°C.

Specifically, the nickel-based catalyst passes through Ce ₂ O ₃ +CO ₂ →2CeO ₂ +CO, 2CeO ₂ +C(s)→Ce ₂ O ₃ +CO, and CO ₂ + C → 2CO three chemical reactions to eliminate carbon deposits.

According to another aspect of the present invention, the present invention also provides a method for preparing a nickel-based catalyst for catalytic methane and carbon dioxide reforming into synthesis gas, the method comprising the following steps:

(1) Dissolving a predetermined amount of carbonate to form a carbonate solution;

(2) dissolving a predetermined amount of soluble nickel salt, soluble magnesium salt, soluble aluminum salt, soluble zirconium salt, soluble molybdenum salt and soluble cerium salt to form a mixed solution;

(3) adding a carbonate solution and an alkali solution to the mixed solution and stirring to obtain a suspension, wherein the addition rate is controlled so that the pH value of the mixed solution is maintained within a predetermined range;

(4) placing the suspension in a crystallization reaction kettle for crystallization treatment, washing the crystallized suspension to neutrality and suction filtration to form a filter cake;

(5) The filter cake is dried at 80°C to 100°C, and then roasted at 700°C to 900°C to obtain a composite oxide;

(6) Reducing the composite oxide by flowing a reducing mixed gas at 900° C. to 1000° C. to obtain the nickel-based catalyst.

Specifically, the soluble nickel salt, soluble magnesium salt, soluble aluminum salt, soluble zirconium salt, soluble molybdenum salt and soluble cerium salt are nitrates, hydrochlorides and sulfates of corresponding metals;

The alkaline solution is any one of sodium hydroxide, potassium hydroxide and ammonium hydroxide or any combination thereof;

The carbonate is any one of sodium carbonate, potassium carbonate, ammonium bicarbonate and ammonium carbonate or any combination thereof;

The pH value is in the range of 8.0 to 11.

Further, the soluble molybdenum salt is ammonium heptamolybdate, the crystallization treatment time is 1-24 hours, the drying time is 1-12 hours, and the roasting time is 6-10 hours,

Carry out in the constant temperature water bath of 60 ℃ when carrying out step (1) and (2); In described step (3), described mixed solution is added dropwise in described sodium carbonate solution, and dropwise adds described Put the alkali solution into the sodium carbonate solution, stir vigorously and keep the pH value in the range of 8.0-11, continue stirring for 1-3 hours after the dropwise addition is completed, and then proceed to step (4).

Specifically, the nickel-based catalyst is used as a diluent through quartz sand before use and reduction,

The method for obtaining the nickel-based catalyst by reduction in step (6) may further comprise the steps:

The nickel-based catalyst and quartz sand are mixed evenly and put into a quartz tube of an atmospheric fixed bed for reaction;

A mixed gas of hydrogen and nitrogen is passed into the quartz tube, and a three-stage heating treatment is carried out, and the three-stage heating treatment includes:

The first stage: from room temperature to 450°C, the heating rate is 5°C/min, and it takes 150 minutes;

The second stage: from 450°C to 900°C, the heating rate is 1°C/min, and it takes 450 minutes;

The third stage: keep the temperature at 900° C. for 120 minutes to obtain the nickel-based catalyst.

Preferably, the gas in the quartz tube is switched to CO ₂ /CH ₄ =1, and the stability and activity of the nickel-based catalyst are measured at a rate of 150 mL/min and a space velocity of 60000 mL/gh ^-1 .

The nickel-based catalyst provided by the embodiments of the present invention and the method for preparing the nickel-based catalyst have at least one of the following advantages:

(1) The nickel-based catalyst of the present invention eliminates carbon deposits by establishing a dynamic equilibrium for autonomously eliminating carbon deposits through oxygen vacancies in Ce ⁴⁺ /Ce ³⁺ and CO ₂ in the reaction atmosphere.

(2) The present invention synthesizes a catalyst with high reactivity, good stability and the dynamic balance of carbon removal through oxygen holes in Ce ⁴⁺ /Ce ³⁺ and reaction atmosphere through co-precipitation method.

(3) When the nickel-based catalyst is used for catalytic reforming of methane and carbon dioxide to produce synthesis gas, the nickel-based catalyst can make the conversion rate of methane and carbon dioxide close to the thermodynamic equilibrium value, and at GHSV (space velocity) = 60000mL/gh ^- At ¹ o'clock, the conversion rate of methane is still maintained at 95-96% after the nickel-based catalyst is used at 900°C for 658 hours, for example. Moreover, the average carbon deposition rate is only 0.017mg _c /g _cat h ^-1 . When the nickel-based catalyst is used at 1000°C, there is no sign of deactivation after 610 hours of use, and the average carbon deposition rate is only 0.0043mg _c /g _cat h ^-1 , thereby solving the problems of quick deactivation and easy carbon deposition of nickel-based catalysts.

Description of drawings

These and/or other aspects and advantages of the present invention will become apparent and comprehensible from the following description of preferred embodiments in conjunction with the accompanying drawings, in which:

Fig. 1 is when using No. 1 nickel-based catalyst provided according to the present invention _The conversion rate view of CH ;

Fig. 2 is when using No. 2 nickel-based catalysts provided according to the present invention _The conversion rate view of CH ;

Fig. 3 is when using No. 3 nickel-based catalysts provided according to the present invention _The conversion rate view of CH ;

Fig. 4 is a comparison chart of the conversion rate of CH ₄ when using the No. 1 nickel-based catalyst provided by the present invention at 900°C and 1000°C.

detailed description

The technical solution of the present invention will be further specifically described below through examples and in conjunction with accompanying drawings 1-4. In the specification, the same or similar reference numerals designate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention, but should not be construed as a limitation of the present invention.

As described in the background section, in order to at least partially overcome the shortcomings of nickel-based catalysts in the prior art, at least one embodiment of the present invention provides a nickel-based catalyst for catalytic reforming of methane and carbon dioxide to produce syngas catalyst. The chemical formula of the nickel-based catalyst is Ni(Mo)/(Cex Zr _{1-x O 2} ) _y MgAl(O), where Ni is the active metal, MO ₃ .MgO and Cex Zr _{1-x O 2} are additives , Al ₂ O ₃ is the carrier, wherein x/1-x=0.25-4, y=1%-15%. Specifically, the precursor of the nickel-based catalyst is NiMgAl-like hydrotalcite. In one embodiment, the nickel-based catalyst comprises 8% to 15% of nickel oxide and 0.2% to 0.70% of molybdenum oxide by mass fraction, and cerium dioxide and zirconium dioxide account for the total mass of the nickel-based catalyst. 1% to 15%. The nickel-based catalyst uses NiMgAl-like hydrotalcite as a precursor, and the catalyst precursor is prepared in one step through a co-precipitation method, and then used after washing, drying and roasting, and performing a reduction reaction in a reducing atmosphere. In an example of the present invention, the reducing atmosphere is a mixed gas of hydrogen and nitrogen, the ratio of hydrogen and nitrogen in the mixed gas is 1:1, and the reduction reaction is carried out at 900-1000°C. Of course, the present invention is not limited here to the combination of hydrogen and nitrogen, any known reducing gas can be used in the present invention.

Specifically, the use condition of the nickel-based catalyst is 850-1050°C.

The nickel-based catalyst passes through Ce ₂ O ₃ +CO ₂ →2CeO ₂ +CO, 2CeO ₂ +C(s)→Ce ₂ O ₃ +CO, CO ₂ +C→2CO under the above-mentioned service conditions (for example, 900°C). Three chemical reactions carry out carbon deposition elimination.

In addition, the present invention also provides a method for preparing the above-mentioned nickel-based catalyst for catalytic reforming of methane and carbon dioxide to produce synthesis gas, the method comprising the following steps:

(1) Dissolving a predetermined amount of carbonate to form a carbonate solution;

(2) dissolving a predetermined amount of soluble nickel salt, soluble magnesium salt, soluble aluminum salt, soluble zirconium salt, soluble molybdenum salt and soluble cerium salt to form a mixed solution;

(3) adding a carbonate solution and an alkali solution to the mixed solution and stirring to obtain a suspension, wherein the addition rate is controlled so that the pH value of the mixed solution is maintained within a predetermined range;

(4) placing the suspension in a crystallization reaction kettle for crystallization treatment, washing the crystallized suspension to neutrality and suction filtration to form a filter cake;

(5) The filter cake is dried at 80°C to 100°C, and then roasted at 700°C to 900°C to obtain a composite oxide;

(6) Reducing the composite oxide by flowing a reducing mixed gas at 900° C. to 1000° C. to obtain the nickel-based catalyst.

In step (2), the soluble nickel salt, soluble magnesium salt, soluble aluminum salt, soluble zirconium salt, soluble molybdenum salt and soluble cerium salt are nitrate, hydrochloride and sulfate of corresponding metals. The alkali solution is any one of sodium hydroxide, potassium hydroxide and ammonium hydroxide or any combination thereof. The carbonate is any one of sodium carbonate, potassium carbonate, ammonium bicarbonate and ammonium carbonate or any combination thereof. Here, it should be noted that the soluble nickel salts, soluble magnesium salts, soluble aluminum salts, soluble zirconium salts, soluble molybdenum salts and soluble cerium salts described here can be dissolved to form a solution, and are not necessarily limited to the above-mentioned exemplified example. Similarly, the alkali solution and the carbonate solution do not necessarily have to be formed from the above-mentioned examples.

Specifically, the pH value is in the range of 8.0 to 11.

In one example, the precursor of ZrO ₂ can be a soluble zirconium salt such as ZrO(NO ₃ ) ₂ xH ₂ O, and the precursor of MoO ₃ is (NH ₃ )Mo ₇ O ₂₄ .4H ₂ O (ammonium heptamolybdate) . In addition, the crystallization treatment time is 1-24 hours, the drying time is 1-12 hours, and the calcination time is 6-10 hours.

When carrying out steps (1) and (2), carry out in the constant temperature water bath of 60 ℃ for example; In described step (3), add described mixed solution dropwise in described sodium carbonate solution, and dropwise add Add the alkali solution into the sodium carbonate solution, stir vigorously and keep the pH value in the range of 8.0-11, continue stirring for 1-3 hours after the dropwise addition is completed, and then proceed to step (4).

In another example, the nickel-based catalyst is passed through quartz sand as a diluent before use and before reduction.

The method for obtaining the nickel-based catalyst by reduction in step (6) may further comprise the steps:

The nickel-based catalyst and quartz sand are mixed evenly and put into a quartz tube of an atmospheric fixed bed for reaction;

A mixed gas of hydrogen and nitrogen is passed into the quartz tube, and a three-stage heating treatment is carried out, and the three-stage heating treatment includes:

The first stage: from room temperature to 450°C, the heating rate is 5°C/min, and it takes 150 minutes;

The second stage: from 450°C to 900°C, the heating rate is 1°C/min, and it takes 450 minutes;

The third stage: keep the temperature at 900° C. for 120 minutes to obtain the nickel-based catalyst.

When measuring the stability and activity of the nickel-based catalyst, the gas in the quartz tube was switched to CO ₂ /CH ₄ =1, and the gas was measured at 150 mL/min with a space velocity of 60000 mL/gh ⁻¹ .

One of the specific examples of the preparation method of the nickel-based catalyst of the present invention by the co-precipitation method using the NiMgAl-like hydrotalcite precursor and the determination method of the stability and activity of the nickel-based catalyst are listed below.

Specifically, a certain amount of Na ₂ CO ₃ was dissolved in 120 mL of deionized water, and placed in a 60°C constant temperature water bath, and then 150 mL of ammonium heptamolybdate, Ni, Mg and Al nitrates, Ce Mix with Zr nitrate to form a mixed salt solution. At the same time, the above mixed salt solution and NaOH solution (2mol/L) were added dropwise into the above sodium carbonate solution, vigorously stirred and the pH value maintained at 8.0-11. Continue to stir for 1-3h after the dropwise addition, then transfer the suspension into a 100mL crystallization kettle, and crystallize in an oven at 80°C for 24 hours. After the crystallization is complete, wash the suspension, filter it with suction, and The filter cake is dried in an oven at 80-100° C. for a certain period of time (for example, 12 hours). Then calcining, specifically calcining at 700-900° C. for 6-10 hours in a muffle furnace to obtain a composite oxide.

It should be noted that in the process of forming the mixed salt solution, the molar ratio of (Ni+Mg)/Al is kept at 3, and the molar ratio of Ce/Zr is kept at 1-4. After calcination, ensure that the total mass fraction of CeO ₂ and ZrO ₂ in the calcination catalyst is 1-15%. During the above dropping process, the amount of substances holding (n(CO ₃ ²⁻ )/n(M ⁿ⁺ ) metal ions=2/3, where M represents various metals.

Catalyst activity and stability evaluation of the present invention is carried out on the reaction device of normal pressure fixed bed (inside diameter is 8mm), weighs catalyst 0.3g and quartz sand 1.5g mixes and puts in the reaction gas of quartz tube. Introduce N ₂ /H ₂ =1 (20mL/min) before the reforming reaction of CH ₄ -CO ₂ , use a temperature program controller to control the temperature, and use a three-stage program to raise the temperature. The first stage: room temperature to 450°C, the heating rate 5℃/min, time-consuming 150min; second stage: 450℃～900℃, heating rate 1℃/min to 900℃, time-consuming 450min; third stage: constant temperature at 900℃ for 120min, Ni(Mo )/( _{CexZr1 - xO2} ) _yMgAl (O) catalyst. Then the gas was switched to CO ₂ /CH ₄ =1 (150 mL/min) and the space velocity was 60000 mL/gh ^-1 to measure the stability and activity of the catalyst.

In order to measure and compare the stability and activity of the nickel-based catalysts provided by the present invention, No. 1 nickel-based catalyst, No. 2 nickel-based catalyst and No. 3 nickel-based catalyst were obtained under the following three different operating conditions.

Example 1 for preparing No. 1 nickel-based catalyst:

Dissolve 9.8g of anhydrous _Na2CO3 in _120mL of deionized water and place in a three-necked flask, weigh 0.036g of ammonium heptamolybdate, 10.5g of aluminum nitrate, 20.2g of magnesium nitrate, 0.13g of cerium nitrate, 2.4g Nickel nitrate, 0.02 g zirconium nitrate and these salts were dissolved in 150 mL deionized water to form a mixed salt solution. Afterwards, the above mixed salt solution and NaOH solution (2mol/L) were added dropwise to the above Na ₂ CO ₃ solution at 60° C., and the pH value was maintained at 9.3 under vigorous stirring. After the dropwise addition, it was fully stirred for 3 hours, then added to a crystallization reaction kettle for crystallization at 80-100°C for 24 hours, then washed until neutral, suction filtered, and the filter cake was dried in an oven at 80-100°C for 24 hours. Then calcined at 800° C. for 10 h in a muffle furnace to obtain the No. 1 nickel-based catalyst.

It should be noted that during the formation of the mixed salt solution, the molar ratio of (Ni+Mg)/Al was kept at 3, and the molar ratio of Ce/Zr was kept at 3. After calcination, ensure that the total mass fraction of CeO ₂ and ZrO ₂ in the calcination catalyst is 1%, the mass fraction of NiO is 12%, and the mass fraction of MoO ₃ is 0.5%. During the above dropping process, the amount of substances holding (n(CO ₃ ²⁻ )/n(M ⁿ⁺ ) metal ions=2/3, where M represents various metals.

Example 2 for preparing No. 2 nickel-based catalyst:

Dissolve 9.7g of anhydrous _Na2CO3 in _120mL of deionized water and place in a three-necked flask, weigh 0.036g, ammonium heptamolybdate, 10.31g of aluminum nitrate, 20.0g of magnesium nitrate, 0.4g of cerium nitrate, 2.4 g nickel nitrate, 0.2 g zirconium nitrate and these salts were dissolved in 150 mL deionized water to form a mixed salt solution. Afterwards, the above mixed salt solution and NaOH solution (2mol/L) were added dropwise to the above Na ₂ CO ₃ solution at 60° C., and the pH value was maintained at 9.5 under vigorous stirring. After the dropwise addition, stir well for 1 hour, then add it into a crystallization reaction kettle for crystallization at 80-100°C for 24 hours, then wash until neutral, filter with suction, and dry the filter cake in an oven at 80-100°C for 24 hours. Then bake it in a muffle furnace at 800°C for 10 hours to prepare the No. 2 nickel-based catalyst.

It should be noted that during the formation of the mixed salt solution, the molar ratio of (Ni+Mg)/Al was kept at 3, and the molar ratio of Ce/Zr was kept at 1. After calcination, ensure that the total mass fraction of CeO ₂ and ZrO ₂ in the calcination catalyst is 5%, the mass fraction of NiO is 12%, and the mass fraction of MoO ₃ is 0.5%. During the above dropping process, the amount of substances holding (n(CO ₃ ²⁻ )/n(M ⁿ⁺ ) metal ions=2/3, where M represents various metals.

Example 3 for preparing No. 3 nickel-based catalyst:

Dissolve 9.48g of anhydrous _Na2CO3 in _120mL of deionized water and place in a three-necked flask, weigh 0.036g of ammonium heptamolybdate, 10.11g of aluminum nitrate, 18.8g of magnesium nitrate, 0.7g of cerium nitrate, 2.4g Nickel nitrate, 1.5 g zirconium nitrate and these salts were dissolved in 150 mL deionized water to form a mixed salt solution. Afterwards, the above mixed salt solution and NaOH solution (2mol/L) were added dropwise to the above Na ₂ CO ₃ solution at 60° C., and the pH value was maintained at 10.0 under vigorous stirring. After the dropwise addition, stir well for 1 hour, then add it into a crystallization reaction kettle for crystallization at 80-90°C for 24 hours, then wash until neutral, filter with suction, and dry the filter cake in an oven at 80-100°C for 24 hours. Then bake it in a muffle furnace at 800° C. for 10 h to prepare the No. 3 nickel-based catalyst.

It should be noted that during the formation of the mixed salt solution, the molar ratio of (Ni+Mg)/Al was kept at 3, and the molar ratio of Ce/Zr was kept at 0.25. After calcination, ensure that the total mass fraction of CeO ₂ and ZrO ₂ in the calcination catalyst is 9%, the mass fraction of NiO is 12%, and the mass fraction of MoO ₃ is 0.5%. During the above dropping process, the amount of substances holding (n(CO ₃ ²⁻ )/n(M ⁿ⁺ ) metal ions=2/3, where M represents various metals.

Weigh 300 mg each of the above No. 1, No. 2 and No. 3 nickel-based catalysts, add 1500 mg of quartz sand as a diluent, grind and press into a quartz tube reactor with an inner diameter of 8 mm, and feed H ₂ /N ₂ (1 : 1), reduced at 900°C for 2 hours. Under normal pressure, CO ₂ /CH ₄ (1:1) was fed into the reactor at a flow rate of 300 ml/min, and the tail gas composition was detected by gas chromatography. The results are shown in Figures 1-3, showing that the use of No. 1, No. 2 and No. 3 catalysts can make the conversion of _CH4 reach more than 90%. Specifically, after 600 hours of use, the conversion rate of methane of No. 1-3 nickel-based catalysts all remained above 90% without obvious carbon deposition.

In addition, 300 mg of the No. 1 nickel-based catalyst was also weighed, and 1500 mg of quartz sand was added as a diluent. After granulation, it was placed in a quartz tube reactor with an inner diameter of 8 mm, and H ₂ /N ₂ (1:1) was introduced. Reduction at 1000°C for 2 hours. Under normal pressure, CO ₂ /CH ₄ (1:1) was fed into the reactor at a flow rate of 300 ml/min, and the tail gas composition was detected by gas chromatography. Combining the above-mentioned measurement experiment results at 900°C, a comparison chart of the conversion rate of CH ₄ under the two conditions of 900°C and 1000°C is obtained. It can be seen from Figure 4 that when the No. 1 nickel-based catalyst was used at 1000°C for 610 hours, there was no sign of deactivation, and the average carbon deposition rate was only 0.0043 mg _c /g _cat h ^-1 .

The nickel-based catalytic performance of the present invention is far superior to catalysts such as traditional Ni/Al ₂ O ₃ , when Ni(Mo)/(Ce _x Zr _1-x O ₂ ) _y MgAl(O) is used for carbon dioxide reforming methane reaction, in Under the reaction conditions of 900°C, CO ₂ : CH ₄ = 1: 1, GHSV = 60000ml/gh ^-1 , the conversion rate of methane can reach more than 95%. There is no deactivation phenomenon, and the conversion rate of methane at 1000°C is maintained at 98-99%, and there is no sign of deactivation after 610 hours.

The dynamic balance of eliminating carbon deposition of the present invention will be described in detail below.

The catalyst of the present invention can build a dynamic equilibrium for eliminating carbon deposits with _CO2 in the reaction gas components. Possible reactions under this system:

CH ₄ +CO ₂ →2CO+2H ₂ (1)

CH ₄ →C+H ₂ (2)

2CO→CO ₂ +C(3)

Ce ₂ O ₃ +CO ₂ →2CeO ₂ +CO(4)

2CeO ₂ +C(s)→2Ce ₂ O ₃ +CO(5)

The carbon deposition in the methane carbon dioxide reforming reaction mainly comes from the cracking reaction of methane (1) and the disproportionation reaction of CO. When the temperature is higher than 700 °C, the disproportionation reaction does not occur, and the main source of carbon deposition mainly comes from the cracking of methane. Since CeO ₂ has oxygen vacancies in Ce ⁴⁺ /Ce ³⁺ , and the lowest thermodynamic temperature of CeO ₂ +C→Ce ₂ O ₃ +CO is 900℃, the reaction of CeO ₂ +Ni→Ce ₂ O ₃ +NiO It cannot occur at low temperature, so the active components are not oxidized while ensuring the elimination of carbon deposits. However, reaction (4) will occur at normal temperature, so in order to build a balance to eliminate carbon deposition, the reaction temperature is selected to be higher than 900°C. Part of the carbon deposit on the surface of the catalyst is removed by CO ₂ +C→2CO (reverse reaction of disproportionation reaction). The other part is removed by reaction (4), and what is reduced to Ce ₂ O ₃ is restored to CeO by reaction ( ₃ ). The carbon deposition on the surface of the equilibrium catalyst is continuously eliminated, and the catalyst returns to the initial state by self-reaction Therefore, the high activity and stability of the catalyst are maintained. Therefore, the catalyst establishes a dynamic equilibrium for eliminating carbon deposits through _CO2 in the reaction atmosphere and _CeO2 in the catalyst.

The nickel-based catalyst provided by the embodiments of the present invention and the method for preparing the nickel-based catalyst have at least one of the following advantages:

(1) The nickel-based catalyst of the present invention establishes a dynamic balance of self-elimination of carbon deposition through the oxygen vacancies in Ce ⁴⁺ /Ce ³⁺ and the reaction atmosphere to eliminate carbon deposition.

(2) The present invention synthesizes a catalyst with high reactivity, good stability and the dynamic balance of carbon removal through oxygen holes in Ce ⁴⁺ /Ce ³⁺ and reaction atmosphere through co-precipitation method.

(3) When the nickel-based catalyst is used for catalytic reforming of methane and carbon dioxide to produce synthesis gas, the nickel-based catalyst can make the conversion rate of methane and carbon dioxide close to the thermodynamic equilibrium value, and at GHSV (space velocity) = 60000mL/gh ^- At ¹ o'clock, the conversion rate of methane remained at 95-96% after the nickel-based catalyst was used at 900° C. for 658 hours. Moreover, the average carbon deposition rate is only 0.017mg _c /g _cat h ^-1 . When the nickel-based catalyst is used at 1000°C, there is no sign of deactivation after 610 hours of use, and the average carbon deposition rate is only 0.0043mg _c /g _cat h ^-1 , thereby solving the problems of quick deactivation and easy carbon deposition of nickel-based catalysts.

It should be noted that, compared with the catalysts known in the prior art, the catalyst provided by the present invention has better catalytic activity because no cerium-zirconium solid solution is formed in the catalyst, but exists in the form of ceria, This is because the method of adding raw materials in the preparation process of the catalyst of the present invention is to form a mixed solution and then precipitate, which is not conducive to the insertion of Zr ⁴⁺ into the crystal lattice of Ce ⁴⁺ to form CeZrO ₂ solid solution. After forming a solid solution, the catalyst is difficult to reduce, resulting in poor activity of the catalyst. In addition, the catalyst is calcined at 800°C, and the higher calcining temperature makes the active metal and the carrier have a strong force. This can increase the stability of the catalyst and reduce the generation of carbon deposits. Finally, the catalyst of the present invention is evaluated above 900° C., at which temperature a dynamic balance of carbon deposits and carbon removal can be established.

While certain embodiments of the present general inventive concept have been shown and described, it will be understood by those of ordinary skill in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept. The scope is defined by the claims and their equivalents.

Claims (10)

1. a nickel-based catalyst for catalytic methane and carbon dioxide reforming synthesis gas, characterized in that, the chemical formula of the nickel-based catalyst is Ni(Mo)/(Cex Zr _{1-x O 2} ) _y MgAl( O), wherein Ni is the active metal, MO ₃ .MgO and Cex Zr _{1-x O 2} are additives, Al ₂ O ₃ is the carrier, wherein x/1-x=0.25～4, y=1%-15 %. 2. the nickel-based catalyst for catalytic methane and carbon dioxide reforming synthesis gas according to claim 1, characterized in that, The nickel-based catalyst includes 8%-15% of nickel oxide and 0.2%-0.70% of molybdenum oxide in terms of mass fraction, and ceria and zirconium dioxide account for 1%-15% of the total mass of the nickel-based catalyst. 3. the nickel-based catalyst for catalytic methane and carbon dioxide reforming synthesis gas according to claim 1 or 2, characterized in that, The nickel-based catalyst uses NiMgAl-like hydrotalcite as a precursor, and the catalyst precursor is prepared in one step by a co-precipitation method, and then used after washing, drying and roasting, and performing a reduction reaction in a reducing atmosphere. 4. the nickel-based catalyst for catalytic methane and carbon dioxide reforming synthesis gas according to claim 3, characterized in that, The reducing atmosphere is a mixed gas of hydrogen and nitrogen, the ratio of hydrogen and nitrogen in the mixed gas is 1:1, and the reduction reaction is carried out at 900-1000°C. 5. the nickel-based catalyst for catalytic methane and carbon dioxide reforming synthesis gas according to claim 4, characterized in that, The nickel-based catalyst passes through Ce ₂ O ₃ +CO ₂ →2CeO ₂ +CO, 2CeO ₂ +C(s)→Ce ₂ O ₃ +CO, and CO ₂ +C→2CO under the use condition of 850-1050°C Three chemical reactions carry out carbon deposition elimination. 6. A method for preparing a nickel-based catalyst for catalytic methane and carbon dioxide reforming synthesis gas according to any one of claims 1-5, said method comprising the following steps: (1) Dissolving a predetermined amount of carbonate to form a carbonate solution; (2) dissolving a predetermined amount of soluble nickel salt, soluble magnesium salt, soluble aluminum salt, soluble zirconium salt, soluble molybdenum salt and soluble cerium salt to form a mixed solution; (3) adding a carbonate solution and an alkali solution to the mixed solution and stirring to obtain a suspension, wherein the addition rate is controlled so that the pH value of the mixed solution is maintained within a predetermined range; (4) placing the suspension in a crystallization reaction kettle for crystallization treatment, washing the crystallized suspension to neutrality and suction filtration to form a filter cake; (5) The filter cake is dried at 80°C to 100°C, and then roasted at 700°C to 900°C to obtain a composite oxide; (6) Reducing the composite oxide by flowing a reducing mixed gas at 900° C. to 1000° C. to obtain the nickel-based catalyst. 7. The method of claim 6, wherein, The soluble nickel salts, soluble magnesium salts, soluble aluminum salts, soluble zirconium salts, soluble molybdenum salts and soluble cerium salts are nitrates, hydrochlorides and sulfates of corresponding metals; The alkaline solution is any one of sodium hydroxide, potassium hydroxide and ammonium hydroxide or any combination thereof; The carbonate is any one of sodium carbonate, potassium carbonate, ammonium bicarbonate and ammonium carbonate or any combination thereof; The pH value is in the range of 8.0 to 11. 8. The method of claim 7, wherein, The soluble molybdenum salt is ammonium heptamolybdate, the crystallization treatment time is 1-24 hours, the drying time is 1-12 hours, and the roasting time is 6-10 hours, Carry out in the constant temperature water bath of 60 ℃ when carrying out step (1) and (2); In described step (3), described mixed solution is added dropwise in described sodium carbonate solution, and dropwise adds described Put the alkali solution into the sodium carbonate solution, stir vigorously and keep the pH value in the range of 8.0-11, continue stirring for 1-3 hours after the dropwise addition is completed, and then proceed to step (4). 9. The method of claim 6, wherein, The nickel-based catalyst is used as a diluent through quartz sand before use and before reduction, The method for obtaining the nickel-based catalyst by reduction in step (6) may further comprise the steps: The nickel-based catalyst and quartz sand are mixed evenly and put into a quartz tube of an atmospheric fixed bed for reaction; A mixed gas of hydrogen and nitrogen is passed into the quartz tube, and a three-stage heating treatment is carried out, and the three-stage heating treatment includes: The first stage: from room temperature to 450°C, the heating rate is 5°C/min, and it takes 150 minutes; The second stage: from 450°C to 900°C, the heating rate is 1°C/min, and it takes 450 minutes; The third stage: keep the temperature at 900° C. for 120 minutes to obtain the nickel-based catalyst. 10. The method of claim 9, wherein, The gas in the quartz tube was switched to CO ₂ /CH ₄ =1, and the stability and activity of the nickel-based catalyst were measured at a rate of 150 mL/min and a space velocity of 60000 mL/gh ^-1 .